1. FIELD OF THE INVENTION
This invention relates to a bearing device adapted to be used for an electronic equipment such as a magnetic disk device.
2. DESCRIPTION OF THE PRIOR ART
FIG. 5 is an explanatory view showing a conventional bearing device used in a carriage feeding mechanism. In FIG. 5, reference numeral 1 designates a base made of aluminum, numeral 2 denotes a stepping motor mounted on the base 1, and numeral 3 depicts a threaded shaft of a rotational shaft formed with spiral threads 3a on the outer periphery thereof. The right end of FIG. 5 of the threaded shaft 3 is rotatably supported to a bearing device 4 as a reference side bearing which consists of a ball 5 disposed in a recess 1a of the base 1, a high hardness retainer 6 and a cylindrical metal 7. The left end of FIG. 5 of the threaded shaft 3 is fixed therethrough a cylindrical permanent magnet 8 of a rotor of the stepping motor 2, and an elastic member 10 applies an axial tension to the threaded shaft 3 through a ball 9. A cylindrical metal 11 is press-fitted to the base 1 disposed on the front face of the stepping motor 2 to position the radial direction of the shaft 3 similarly to the metal 7. Numeral 12 designates a coil of a stator of the stepping motor 2 and numeral 13 denotes a coil bobbin.
A slide bearing such as an inexpensive metal has been used instead of an expensive ball bearing to reduce its cost as a bearing device of a threaded shaft.
However, since the above-described bearing device 4 is constructed by press-fitting the metal 7 after inserting the retainer 6 into the recess 1a of the bottom of the base 1, it has such drawbacks that machining of finishing the inner diameter of the metal 7 in a predetermined size after press-fitting and raising the coaxial degree of the metal 11, i.e., the sizing enabling by passing the base 1 with a cutting tool cannot be executed. When the sizing work cannot be done, an accurate dimension of the bearing device cannot only be provide,, but the accuracy of drilling of the recess 1a of the base 1 and the dimensional accuracy of the metals 7, 11 before press-fitting must be raised more than required, resulting in an increase in its cost.